1. Field of Endeavor
The present invention relates to porous carbon fuel particles and more particularly to protection of porous carbon fuel particles from Boudouard corrosion.
2. State of Technology
U.S. Pat. No. 8,153,328 for carbon fuel cells with carbon corrosion suppression issued Apr. 10, 2012 to John F. Cooper provides the following information on the state of technology:
“Direct Carbon Conversion (DCC) fuel cells and batteries make use of carbon anodes in the form of porous plates or paste-like powders of carbon particles mixed with molten salts at 650-850 C. Near to the reacting interface, the anode reaction is typically C+2CO32−=3CO2+4e−. This reaction yields CO2 (and not CO) because the anode surface is polarized and covered with an adherent layer of R—CO functional groups that inhibit the anodic reaction on an otherwise bare surface that would yield CO. Evolution of CO (and not C02) would cut the total electrochemical efficiency roughly in half. Far from the reacting surface, Boudouard corrosion (C+CO2=2CO) takes place, reducing the total electrochemical efficiency by a factor of two.”“During the refueling of a fuel cell (and the manufacture of carbon primary batteries), the fuel cell anode chamber is filled with carbon that will be reacted over an extended period of time. The reaction of the carbon in the reaction zone extending a few millimeters from the anode current collector into the bulk of the carbon produces CO2. It is important that this CO2 not be allowed to flow through or pass over that portion of the carbon that is not polarized. A system for exhausting the carbon dioxide from the anode chamber without flowing through the bulk of the unreacted carbon fuel is needed to bring the system to maximum efficiency. Further, some CO will invariably be produced by contacting the carbon with the CO2 or by electrochemical reaction at currents below those required for polarization. A system for recovering the energy associated with the formation of CO is also helpful in achieving maximum efficiency of the cell.”
U.S. Pat. No. 6,815,105 for a fuel cell apparatus and method thereof issued Nov. 9, 2004 to John F. Cooper, Roger Krueger, and Nerine Cherepy provides the following information on the state of technology:
“High temperature, molten electrolyte, electrochemical cells have been shown to be an efficient method of producing energy particularly when the fuel source is hydrogen gas. Carbon as a fuel source in electrochemical cells has been explored. Efficiencies of various carbon sources have been calculated based on half-cell data and have consistently been low, e.g., 50% or less.”“Aspects of the invention include a high temperature, molten electrolyte electrochemical cell comprising ash-free, turbostratic carbon particles.”“Another aspect of the invention includes a high temperature, molten electrolyte, electrochemical cell for directly converting a carbon fuel to electrical energy, the electrochemical cell comprising a cathode compartment having an oxygen-containing gas and a molten electrolyte; an anode compartment having a slurry comprising the molten electrolyte and carbon particles entrained in the molten electrolyte; and an electron insulating, ion conducting, porous ceramic separator between the cathode compartment and the anode compartment.”“Another aspect of the invention includes a high temperature, molten electrolyte electrochemical cell for directly converting a carbon fuel to electrical energy, the electrochemical cell comprising a cathode compartment formed by a housing comprising non-porous, inert material having a gas inlet and outlet, an oxygen-containing gas, a molten electrolyte, and a cathode current collector; an anode compartment having an inlet, an anode current collector, and a slurry comprising the molten electrolyte and carbon particles entrained in the molten electrolyte; and an electron insulating, ion conducting, porous ceramic separator between the cathode compartment and the anode compartment, the porous ceramic separator capable of allowing transport of ions produced in the cathode compartment to the slurry.”“Another aspect of the invention includes a method for producing electrical energy, the method comprising the steps of heating an electrochemical cell containing a carbon fuel entrained in an electrolyte to an operating temperature; producing carbonate ions by bringing an oxygen-containing gas in contact with a cathode current collector wetted with molten carbonate; transporting the carbonate ions through a porous ceramic separator to an anode current collector; reacting the carbonate ions with the carbon fuel; and collecting the electrical energy produced through the anode current collector.”
U.S. Pat. No. 6,878,479 for a tilted fuel cell apparatus issued Apr. 12, 2005 to John F. Cooper, Nerine Cherepy, and Roger Krueger provides the following information on the state of technology:
“An aspect of the invention includes an apparatus comprising: an anode current collector; a cathode current collector; a porous ceramic separator, wherein the separator is sandwiched between the cathode current collector and the anode current collector and the anode current collector is at a higher elevation than the cathode current collector; an anode plate and rib assembly comprising a plate and a plurality of ribs, wherein the anode plate and rib assembly is positioned such that the ribs are electrically connected to the anode current collector to form a plurality of anode channels; a cathode plate and rib assembly comprising a plate and a plurality of ribs, wherein the cathode plate and rib assembly is positioned such that the ribs are electrically connected to the cathode current collector to form a plurality of cathode channels; means for entry to the anode channels of a plurality of particles, wherein the particles consist essentially of carbon, electrolyte, or mixtures thereof; means for entry of a gas containing both oxygen and carbon-dioxide to the cathode channels; means for exit of carbon dioxide gas and excess molten electrolyte from the anode channels; and means for exit of gaseous byproducts and excess molten electrolyte from the cathode channels, wherein the cell assembly is substantially planar and rectangular and tilted at an acute angle to the horizontal in a configuration such that the means of entry are positioned at a higher elevation than the means of exit and that the anode plate and rib assembly is positioned at a higher elevation than the cathode plate and rib assembly.”“Another aspect of the invention includes An apparatus comprising: at least two bipolar, high temperature, molten electrolyte cell assemblies, wherein each cell assembly comprises: a porous ceramic separator; a cathode current collector; an anode current collector, wherein the separator is sandwiched between the cathode current collector and the anode current collector and the anode current collector is at a higher elevation than the cathode current collector; a cathode plate and rib assembly comprising a plate and a plurality of ribs, wherein the cathode plate and rib assembly is positioned such that the ribs are in contact with the cathode current collector and form a plurality of cathode channels; an anode plate and rib assembly comprising a plate and a plurality of ribs, wherein the anode plate and rib assembly is positioned such that the ribs are in contact with the anode current collector and form a plurality of anode channels; means for entry to the anode channels of a plurality of particles, wherein the particles consist essentially of carbon, electrolyte, or mixtures thereof; means for entry of a gas containing oxygen and carbon-dioxide to the cathode channels; means for exit of carbon dioxide gas from the anode channels; and means for exit of gaseous byproducts from the cathode channels, wherein the cell assembly is substantially planar and rectangular and tilted at an acute angle to the horizontal in a configuration such that the means of entry are positioned at a higher elevation than the means of exit; and wherein the cell assemblies are connected in electrical series.”